An automotive modular fuel delivery system described in U.S. Pat. No. 4,945,884, issued 7 Aug. 1990 and assigned to the assignee of this invention, includes a reservoir in the fuel tank of the vehicle, an electric fuel pump in the reservoir, and a jet pump for pumping bulk fuel from the tank into the reservoir. A fraction of the high pressure output of the fuel pump is diverted to the jet pump as the energy source for the latter and the remainder is conducted to the engine of the vehicle. Fuel not consumed by the engine is returned, usually hot, to the reservoir. During a prolonged period of low engine fuel consumption, return fuel and jet pump discharge may overflow the reservoir through a vent or other opening between the reservoir and the fuel tank causing a mixing of hot return fuel and bulk fuel in the tank. A modular fuel delivery system according to this invention minimizes the likelihood of overflow from the reservoir into the bulk fuel in the fuel tank thereby to remove a bulk fuel heat source for the purpose of retarding vapor generation in the fuel tank.